There are widespread industrial applications where abrasive articles are needed to produce a desired surface finish. Specific applications include, for example, the polishing of glossy surfaces found in automotive and marine clearcoat finishes and lacquer finishes. Other applications include cleaning or scuffing operations on the surfaces of metals, woods, plastics, and composites. To produce a desired surface finish, service providers often use flexible abrasive pads, which can be manipulated by hand or using a motorized power tool. Such abrasive pads are capable of removing material from the surface of a workpiece (or substrate) in a controlled fashion to remove minor defects.
Certain abrasive articles, generically referred to as “structured abrasive” articles, have been sold commercially for use in the manufacture and repair of glossy surface finishes. These articles have a structured abrasive layer affixed to a backing, where the structured abrasive layer represents a plurality of tiny, shaped abrasive composites, characterized by abrasive particles embedded in a polymeric binder. The shaped abrasive composites can be formed into pyramids or other precise geometric shapes. Examples of such structured abrasive articles include those marketed under the trade designation “TRIZACT,” by 3M Company, St. Paul, Minn.
Alternatively, abrasive articles can be made by coating a sequence of layers onto a flexible backing, such as paper, to form a coated abrasive. For example, a first resin can be initially deposited onto the backing to provide a make coat. Abrasive grains are then added and tacked down to the backing by the make coat. A second resin, called a size coat, is then coated over both the make coat and the abrasive particles. Optionally, additional coats can be added. When hardened, the resins effectively secure the particles to the backing.
In many applications, the flexible abrasive article is moistened with water or some other liquid, optionally containing a surfactant, which acts to lubricate and remove swarf and debris from the abrading surfaces. Two problems are known to arise when performing these so called wet sanding operations. The first is known as “stiction,” a phenomenon where the damp abrasive tends to bind and “stick” to the workpiece as a result of surface tension. Stiction can result in loss of user control over the abrading operation and consequent damage to the workpiece. The second is hydroplaning, which occurs when the abrasive and workpiece become separated by a thin layer of the liquid. This can cause the abrasive to skid across the surface without directly contacting the workpiece, degrading cut performance.